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<h3><a name="SECTION0016312000000000000000"></a><a name="optparse-what-options-for"></a>
<br>
14.3.1.2 What are options for?
</h3>

<p>
Options are used to provide extra information to tune or customize the
execution of a program.  In case it wasn't clear, options are usually
<em>optional</em>.  A program should be able to run just fine with no options
whatsoever.  (Pick a random program from the <span class="Unix">Unix</span> or GNU toolsets.  Can
it run without any options at all and still make sense?  The main
exceptions are <code>find</code>, <code>tar</code>, and <code>dd</code>--all of which are mutant
oddballs that have been rightly criticized for their non-standard syntax
and confusing interfaces.)

<p>
Lots of people want their programs to have ``required options''.  Think
about it.  If it's required, then it's <em>not optional</em>!  If there is a
piece of information that your program absolutely requires in order to
run successfully, that's what positional arguments are for.

<p>
As an example of good command-line interface design, consider the humble
<code>cp</code> utility, for copying files.  It doesn't make much sense to try to
copy files without supplying a destination and at least one source.
Hence, <code>cp</code> fails if you run it with no arguments.  However, it has a
flexible, useful syntax that does not require any options at all:
<div class="verbatim"><pre>
cp SOURCE DEST
cp SOURCE ... DEST-DIR
</pre></div>

<p>
You can get pretty far with just that.  Most <code>cp</code> implementations
provide a bunch of options to tweak exactly how the files are copied:
you can preserve mode and modification time, avoid following symlinks,
ask before clobbering existing files, etc.  But none of this distracts
from the core mission of <code>cp</code>, which is to copy either one file to
another, or several files to another directory.

<p>

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